City report · Colorado, United States
Thornton Air quality today
Air quality in Thornton currently reads AQI 132 (Unhealthy for sensitive groups): Sensitive groups should limit long or intense outdoor activity.
Air quality right now
AQI 132
Unhealthy for sensitive groups
- PM2.5, fine particles (µg/m³)
- 20.9
- tree cover
- 10.3%
- trees in this area
- 32.3K
- more trees needed
- 77.4K
Measured across a 1.2 mi (2 km) radius around Thornton, CO, USA (4.9 sq mi), from a satellite image of Sep 9, 2026. Lower AQI is better: 0–50 is Good, above 300 is Hazardous.
Thornton · AQI 132 (Unhealthy for sensitive groups)
Thornton's tree count comes to 32,261 trees across 4.8 sq mi (12.53 km²) of land, 25 points below the 35% tree-cover level considered healthy for this area, so roughly 77,365 more trees would close the gap.
Air quality detail
Air quality in Thornton today: AQI 132, Unhealthy for sensitive groups
Main pollutant: PM10 · Observed Nov 11, 08:00 local time via OpenAQ ground stations, US EPA index. Values in µg/m³.
Ground station · Adams-Birch, 3.4 mi (5.4 km) away · median of 2 stations
Health signal
Sensitive groups should limit long or intense outdoor activity.
PM2.5
20.9
PM10
217.0
NO₂
74.1
O₃
3.9
SO₂
6.5
CO
—
Data: OpenAQ · AirNow
- Outdoor exercise
- Children, older adults and people with asthma or heart disease should cut down long or hard exercise
- Windows
- Close them to keep the outside air out
- Mask
- Sensitive groups: an N95 outdoors
- Air purifier
- Run one, especially in bedrooms
Over the last 7 days, the CAMS air-quality model put Thornton's daily AQI at 60 on average, from 53 on Nov 8 to an hourly peak of 83 on Nov 5.
Where Thornton stands: the most polluted cities in the world right now · the cleanest
Tree cover detail
Tree cover in Thornton: Critically low
10.3% tree cover against a 35% healthy-neighborhood target, across 4.8 sq mi (12.53 km²) of land.
Trees in this area
32,261
Target trees
109,626
More trees needed
77,365
CO₂ if planted / yr
1,702 t
Deforestation · 2001–2025
How much forest has Thornton lost?
There was very little forest around Thornton in 2000, about 46 acres (19 hectares), and about 7 acres (3 hectares) of it has been lost since. Only fairly dense woodland counts as forest in these maps, so scattered street and garden trees don't show up here.
2017: satellite photo from June 2017 of a 5 × 5 km area in the city center.
Acres of forest lost each year
Show the figures as a table
| Year | Cleared for good | Can grow back | Total |
|---|---|---|---|
| 2001 | under 1 ha | under 1 ha | under 1 ha |
| 2002 | under 1 ha | under 1 ha | under 1 ha |
| 2003 | under 1 ha | under 1 ha | under 1 ha |
| 2004 | under 1 ha | under 1 ha | under 1 ha |
| 2005 | under 1 ha | under 1 ha | under 1 ha |
| 2006 | under 1 ha | under 1 ha | under 1 ha |
| 2007 | under 1 ha | under 1 ha | under 1 ha |
| 2008 | under 1 ha | under 1 ha | under 1 ha |
| 2009 | under 1 ha | under 1 ha | under 1 ha |
| 2010 | under 1 ha | under 1 ha | under 1 ha |
| 2011 | under 1 ha | under 1 ha | under 1 ha |
| 2012 | under 1 ha | under 1 ha | under 1 ha |
| 2013 | under 1 ha | under 1 ha | under 1 ha |
| 2014 | under 1 ha | under 1 ha | under 1 ha |
| 2015 | under 1 ha | under 1 ha | under 1 ha |
| 2016 | under 1 ha | under 1 ha | under 1 ha |
| 2017 | under 1 ha | under 1 ha | under 1 ha |
| 2018 | under 1 ha | under 1 ha | under 1 ha |
| 2019 | under 1 ha | under 1 ha | under 1 ha |
| 2020 | under 1 ha | under 1 ha | under 1 ha |
| 2021 | under 1 ha | under 1 ha | under 1 ha |
| 2022 | under 1 ha | under 1 ha | under 1 ha |
| 2023 | under 1 ha | under 1 ha | under 1 ha |
| 2024 | under 1 ha | under 1 ha | under 1 ha |
| 2025 | under 1 ha | under 1 ha | under 1 ha |
What is causing deforestation around Thornton?
- Mining and energycleared for good37% · 2 acres (1 ha)
- Farms, pasture and plantationscleared for good3.7% · under 1 ha
- Towns and roadscleared for good3.7% · under 1 ha
Also: unknown causes.
Causes for 2025 are estimates, based on what caused forest loss in the same places up to 2024.
Forest gained and lost, 2000–2020
- Forest in 2000
- 1,980 acres (800 ha)
- Forest in 2020
- 3,140 acres (1,270 ha)
- Overall change
- +1,160 acres (470 ha)more forest than in 2000
Comparing satellite maps from 2000 and 2020, the forest around Thornton grew from about 1,980 acres (800 hectares) to 3,140 acres (1,270 hectares), a net gain of about 1,160 acres (470 hectares) (+59%). New forest grew on about 1,170 acres (474 hectares), while 10 acres (4 hectares) were lost.
These 2000 and 2020 maps, from the University of Maryland, count any land with trees taller than 5 m as forest, including plantations and orchards. Forest that was cut or burned and had grown back by 2020 counts in both years, so the loss here is smaller than the yearly figures.
These figures cover everything within 10 km of the city center, a wider area than the report above, because forest is usually lost at a city's edges.
Source: Hansen/UMD/Google/USGS/NASA, Global Forest Change (GFC-2025-v1.13); causes: WRI/Google DeepMind drivers of forest loss; both CC BY 4.0, summed by Airleaf for each area. Forest gained and lost 2000–2020: Potapov et al. 2022, UMD GLAD Global Land Cover and Land Use Change, CC BY 4.0. Images: contains modified Copernicus Sentinel data. How it's measured
In the same region
Measured cities near Thornton
Same 2 km radius, same index — so they compare directly.
- Arvada12.2 km
United States
- Tree cover
- 21%
- Air quality
- 32
- Denver14.4 km
United States
- Tree cover
- 13%
- Air quality
- 29
- Aurora19.5 km
United States
- Tree cover
- 14%
- Air quality
- 23
- Lakewood20.4 km
United States
- Tree cover
- 27%
- Air quality
- 32
- Boulder30.3 km
United States
- Tree cover
- 38%
- Air quality
- 14
- Centennial33.1 km
United States
- Tree cover
- 19%
- Air quality
- 34
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Frequently asked
Questions about Thornton
What is the air quality (AQI) in Thornton right now?
The latest reading for Thornton shows an AQI of 132 (Unhealthy for sensitive groups), measured Nov 11, 08:00 local time by 2 ground monitoring stations via OpenAQ (the median of their readings; the nearest is Adams-Birch, 3.4 mi (5.4 km) away). The main pollutant is PM10. Sensitive groups should limit long or intense outdoor activity.
Is it safe to exercise outside in Thornton today?
At AQI 132 (Unhealthy for sensitive groups): children, older adults and people with asthma or heart disease should cut down long or hard exercise. Windows: close them to keep the outside air out. Masks: sensitive groups: an N95 outdoors. The reading changes through the day, so check again before a long run or ride.
What has the air quality in Thornton been like this week?
Over the last 7 days, the CAMS air-quality model put Thornton's daily AQI at 60 on average, from 53 on Nov 8 to an hourly peak of 83 on Nov 5. No day averaged above 100, the level where the air turns unhealthy for sensitive groups.
How much forest has the area around Thornton lost since 2001?
There was very little forest around Thornton in 2000, about 46 acres (19 hectares), and about 7 acres (3 hectares) of it has been lost since. Only fairly dense woodland counts as forest in these maps, so scattered street and garden trees don't show up here. Comparing satellite maps from 2000 and 2020, the forest around Thornton grew from about 1,980 acres (800 hectares) to 3,140 acres (1,270 hectares), a net gain of about 1,160 acres (470 hectares) (+59%). New forest grew on about 1,170 acres (474 hectares), while 10 acres (4 hectares) were lost.
What is the tree count in Thornton?
Thornton has an estimated 32,261 trees across the 4.8 sq mi (12.53 km²) of land measured — 10.3% tree cover, 25 percentage points short of the 35% tree-cover target set for this area.
How many more trees does Thornton need?
Thornton needs roughly 77,365 more trees to close a 25-point shortfall against its 35% tree-cover target — about 1,702 t of extra CO₂ absorbed per year once grown.
How are Thornton's air quality and tree cover measured?
Air quality is measured by ground monitoring stations near Thornton, via OpenAQ; the 7-day trend is the Open-Meteo / CAMS model's estimate. Tree cover is measured from Sentinel-2 L2A (ESA Copernicus) via Earth Search satellite imagery at 10 m detail across a 1.2 mi (2 km) radius around Thornton; the tree count is an estimate derived from that cover.
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